P122. Use of a novel allograft in single- and two-level posterolateral lumbar spinal fusion: two-year clinical and radiographic results from a prospective multicenter study

BACKGROUND CONTEXT Instrumented posterolateral lumbar fusion (PLF) surgery is commonly used to alleviate pain and other symptoms associated with degenerative conditions of the lumbosacral spine. Although autologous iliac crest bone graft (ICBG) remains the gold standard graft material for PLF, surgeons have sought alternatives to avoid morbidities associated with ICBG harvest. OSTEOAMP® is a novel allograft bone graft substitute (BGS) that retains multiple endogenous growth factors. Evidence concerning effectiveness of PLF in multi-level fusion is scarce. PURPOSE The purpose of this study was to compare 2-year clinical and radiographic outcomes of OSTEOAMP and ICBG in single- and 2-level PLF. STUDY DESIGN/SETTING This was a prospective multicenter cohort study (level 2 evidence) involving nine centers in the United States. PATIENT SAMPLE A total of 42 patients with Oswestry Disability Index (ODI) score of at least 30 at baseline were prospectively enrolled and underwent a single- (N=26) or two-level (N=16) PLF utilizing the novel BGS. 38/42 (90.5%) and 32/42 (76.2%) subjects attended 12- and 24-month follow-ups, respectively. OUTCOME MEASURES ODI, SF-36v2 PCS, SF-36v2 MCS, back and leg pain. METHODS Data was obtained preoperatively and at 1.5, 3, 6, 12, and 24 months. Radiographic studies were assessed by an independent core lab for evidence of bridging bone and lack of segmental angular ( RESULTS The two-year fusion rate for the novel BGS was 32/37 (86.5%) compared to the literature average of 76% (range 40%-100%) for ICBG. The fusion rate was 90.9% (20/22) in single- and 80% (12/15) in 2-level PLF (p=0.377). While ODI improved in both groups, the improvement was larger in single- than in 2-level subjects (p=0.058). At 24 months, the improvement in ODI was 33.5 and 25.9 in single- and 2-level subjects, respectively.  There was a tendency for greater improvements at 24 months in single-level compared to 2-level PLF in SF36 PCS (15.4 vs 12.5) and SF36MCS (7.9 vs 5.6), but these differences did not reach statistical significance. Improvements in pain at back (4.8 vs 4.6) and pain at leg (4.8 vs 4.3) were similar in single- and 2-level surgeries. One secondary surgery was performed at 3 months postoperatively for a symptomatic screw in single-level subject. No product-related treatment complications were reported. CONCLUSIONS Two-level PLF is associated with poorer ODI but similar pain outcomes compared to single-level PLF. OSTEOAMP is safe and effective for use in posterolateral spinal fusion as evidenced by fusion rates higher than for ICBG, good clinical outcomes, and freedom from serious product-related complications. FDA DEVICE/DRUG STATUS OSTEOAMP® is compliant to 21 CFR 1271 and is regulated as a 361 HCT/P.